The following description is provided to assist the understanding of the reader. None of the information provided or references cited is admitted to be prior art.
Different types of acoustic devices have been used through the years. One type of device is a microphone. In a microelectromechanical system (MEMS) microphone, a MEMS die includes at least one diaphragm and at least one back plate. The MEMS die is supported by a substrate and enclosed by a housing (e.g., a cup or cover with walls). A port may extend through the substrate (for a bottom port device) or through the top of the housing (for a top port device). In any case, sound energy traverses through the port, moves the diaphragm and creates a changing potential of the back plate, which creates an electrical signal. Microphones are deployed in various types of devices such as personal computers or cellular phones.
Differential signals are often desired by users. In one example, a first transducer obtains a first differential signal and a second transducer obtains a second differential signal. The second signal is 180 degrees (or approximately 180 degrees) out of phase from the first signal and of the same magnitude. The signals are subtracted from each other to produce an output signal. The subtraction operation removes noise and other undesirable effects from the individual signals and can produce a larger and stronger output signal. However, these approaches at obtaining differential signals require the use of two transducers, which can be expensive and increase the size of the overall device. The problems of previous approaches have resulted in some user dissatisfaction with these previous approaches.